{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T09:05:41Z","timestamp":1779872741463,"version":"3.53.1"},"reference-count":21,"publisher":"PeerJ","license":[{"start":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T00:00:00Z","timestamp":1779840000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"\n Objective<\/jats:title>\n This study investigated electrolyte and acid\u2013base alterations and their associations with performance in 40 Brazilian male runners during a 45-km mountain ultramarathon.<\/jats:p>\n <\/jats:sec>\n \n Method<\/jats:title>\n \n The following parameters were assessed before and after the race: pH, sodium (Na\n +<\/jats:sup>\n ), potassium (K\n +<\/jats:sup>\n ), calcium (Ca\n 2+<\/jats:sup>\n ), glucose, carbon dioxide pressure (pCO\n 2<\/jats:sub>\n ), partial pressure of oxygen (pO\n 2<\/jats:sub>\n ), bicarbonate (HCO\n 3<\/jats:sub>\n ), hematocrit and lactate.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Potassium levels decreased significantly across all performance groups (Fastest:\n p<\/jats:italic>\n \u00a0=\u00a00.004; Moderate-Fast:\n p<\/jats:italic>\n \u00a0=\u00a00.004; Moderate-Slow:\n p<\/jats:italic>\n \u00a0=\u00a00.003; Slowest:\n p<\/jats:italic>\n \u00a0=\u00a00.004), while lactate increased in the Fastest (\n p<\/jats:italic>\n \u00a0=\u00a00.03), Moderate-Fast (\n p<\/jats:italic>\n \u00a0=\u00a00.002), and Slowest (\n p<\/jats:italic>\n \u00a0=\u00a00.03) groups. Sodium increased in the Moderate-Fast group (\n p<\/jats:italic>\n \u00a0=\u00a00.005), whereas calcium decreased in the Slowest group (\n p<\/jats:italic>\n \u00a0=\u00a00.005). Both pCO\n 2<\/jats:sub>\n and HCO\n 3<\/jats:sub>\n were significantly reduced across all groups (pCO\n 2<\/jats:sub>\n :\n p<\/jats:italic>\n \u00a0= 0.0003\u20130.0005; HCO\n 3<\/jats:sub>\n :\n p<\/jats:italic>\n \u00a0= 0.003\u20130.0004), and pH decreased in the Slowest group (\n p<\/jats:italic>\n \u00a0=\u00a00.01). Between-group differences were observed between Fastest and Slowest for pH (\n p<\/jats:italic>\n \u00a0=\u00a00.02), pCO\n 2<\/jats:sub>\n (p = 0.001), and K\n +<\/jats:sup>\n (\n p<\/jats:italic>\n \u00a0<\u00a00.001), and between Fastest and Moderate-Slow for Na\n +<\/jats:sup>\n (\n p<\/jats:italic>\n \u00a0=\u00a00.03). Negative correlations were found between race time and post-race pH (\n R<\/jats:italic>\n \u00a0= \u22120.46), Ca\n 2+<\/jats:sup>\n (\n R<\/jats:italic>\n \u00a0= \u22120.33), and Na\n +<\/jats:sup>\n (\n R<\/jats:italic>\n \u00a0= \u22120.31). In the Slowest group, \u0394 K\n 2+<\/jats:sup>\n was strongly correlated with race time (\n R<\/jats:italic>\n \u00a0= \u22120.83;\n p<\/jats:italic>\n \u00a0=\u00a00.003).\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n Performance in a 45-km mountain ultramarathon appears to be closely associated with the ability to preserve acid\u2013base and electrolyte homeostasis, particularly regarding potassium, sodium, calcium and pH.<\/jats:p>\n <\/jats:sec>","DOI":"10.7717\/peerj.21308","type":"journal-article","created":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T08:33:23Z","timestamp":1779870803000},"page":"e21308","source":"Crossref","is-referenced-by-count":0,"title":["Electrolyte imbalance markers and acid\u2013base disturbances in Brazilian male runners during a 45-km mountain ultramarathon"],"prefix":"10.7717","volume":"14","author":[{"given":"Marcelo Romanovitch","family":"Ribas","sequence":"first","affiliation":[{"name":"Universidade Tecnologica Federal do 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